Multiview-related supplementary enhancement information messages

ABSTRACT

Aspects of the disclosure provide a method, an apparatus, and non-transitory computer-readable storage medium for video decoding. The apparatus includes processing circuitry configured to receive a first supplemental enhancement information (SEI) message including scalability dimension information (SDI). The first SEI message includes SDI of a plurality of views in a multiview bitstream including a coded video sequence (CVS) with a plurality of layers. The processing circuitry determines a value of a first syntax element sdi_view_id_val[] in the first SEI message. The first syntax element sdi_view_id_val[ ] indicates a view identifier (ViewId) of a layer in the plurality of layers. The processing circuitry determines, based on the first syntax element sdi_view_id_val[ ], a target layer of the plurality of layers to which a second syntax element of a second SEI message applies. The first syntax element sdi_view_id_val[] indicates a view of the plurality of views associated with the second syntax element.

INCORPORATION BY REFERENCE

This present disclosure claims the benefit of priority to U.S.Provisional Application No. 63/215,941, “Techniques forMultiview-Related SEI Messages in Coded Video Stream” filed on Jun. 28,2021, which is incorporated by reference herein in its entirety.

TECHNICAL FIELD

The present disclosure describes embodiments generally related to videocoding.

BACKGROUND

The background description provided herein is for the purpose ofgenerally presenting the context of the disclosure. Work of thepresently named inventors, to the extent the work is described in thisbackground section, as well as aspects of the description that may nototherwise qualify as prior art at the time of filing, are neitherexpressly nor impliedly admitted as prior art against the presentdisclosure.

Image and/or video coding and decoding can be performed usinginter-picture prediction with motion compensation. Uncompressed digitalimage and/or video can include a series of pictures, each picture havinga spatial dimension of, for example, 1920×1080 luminance samples andassociated chrominance samples. The series of pictures can have a fixedor variable picture rate (informally also known as frame rate), of, forexample 60 pictures per second or 60 Hz. Uncompressed image and/or videohas specific bitrate requirements. For example, 1080p60 4:2:0 video at 8bit per sample (1920×1080 luminance sample resolution at 60 Hz framerate) requires close to 1.5 Gbit/s bandwidth. An hour of such videorequires more than 600 GBytes of storage space.

One purpose of image and/or video coding and decoding can be thereduction of redundancy in the input image and/or video signal, throughcompression. Compression can help reduce the aforementioned bandwidthand/or storage space requirements, in some cases by two orders ofmagnitude or more. Although the descriptions herein use videoencoding/decoding as illustrative examples, the same techniques can beapplied to image encoding/decoding in similar fashion without departingfrom the spirit of the present disclosure. Both lossless compression andlossy compression, as well as a combination thereof can be employed.Lossless compression refers to techniques where an exact copy of theoriginal signal can be reconstructed from the compressed originalsignal. When using lossy compression, the reconstructed signal may notbe identical to the original signal, but the distortion between originaland reconstructed signals is small enough to make the reconstructedsignal useful for the intended application. In the case of video, lossycompression is widely employed. The amount of distortion tolerateddepends on the application; for example, users of certain consumerstreaming applications may tolerate higher distortion than users oftelevision distribution applications. The compression ratio achievablecan reflect that: higher allowable/tolerable distortion can yield highercompression ratios.

A video encoder and decoder can utilize techniques from several broadcategories, including, for example, motion compensation, transform,quantization, and entropy coding.

Video codec technologies can include techniques known as intra coding.In intra coding, sample values are represented without reference tosamples or other data from previously reconstructed reference pictures.In some video codecs, the picture is spatially subdivided into blocks ofsamples. When all blocks of samples are coded in intra mode, thatpicture can be an intra picture. Intra pictures and their derivationssuch as independent decoder refresh pictures, can be used to reset thedecoder state and can, therefore, be used as the first picture in acoded video bitstream and a video session, or as a still image. Thesamples of an intra block can be exposed to a transform, and thetransform coefficients can be quantized before entropy coding. Intraprediction can be a technique that minimizes sample values in thepre-transform domain. In some cases, the smaller the DC value after atransform is, and the smaller the AC coefficients are, the fewer thebits that are required at a given quantization step size to representthe block after entropy coding.

Traditional intra coding such as known from, for example MPEG-2generation coding technologies, does not use intra prediction. However,some newer video compression technologies include techniques thatattempt, from, for example, surrounding sample data and/or metadataobtained during the encoding and/or decoding of spatially neighboring,and preceding in decoding order, blocks of data. Such techniques arehenceforth called “intra prediction” techniques. Note that in at leastsome cases, intra prediction is using reference data only from thecurrent picture under reconstruction and not from reference pictures.

There can be many different forms of intra prediction. When more thanone of such techniques can be used in a given video coding technology,the technique in use can be coded in an intra prediction mode. Incertain cases, modes can have submodes and/or parameters, and those canbe coded individually or included in the mode codeword. Which codewordto use for a given mode, submode, and/or parameter combination can havean impact in the coding efficiency gain through intra prediction, and socan the entropy coding technology used to translate the codewords into abitstream.

A certain mode of intra prediction was introduced with H.264, refined inH.265, and further refined in newer coding technologies such as jointexploration model (JEM), versatile video coding (VVC), and benchmark set(BMS). A predictor block can be formed using neighboring sample valuesbelonging to already available samples. Sample values of neighboringsamples are copied into the predictor block according to a direction. Areference to the direction in use can be coded in the bitstream or mayitself be predicted.

Referring to FIG. 1A, depicted in the lower right is a subset of ninepredictor directions known from H.265's 33 possible predictor directions(corresponding to the 33 angular modes of the 35 intra modes). The pointwhere the arrows converge (101) represents the sample being predicted.The arrows represent the direction from which the sample is beingpredicted. For example, arrow (102) indicates that sample (101) ispredicted from a sample or samples to the upper right, at a 45 degreeangle from the horizontal. Similarly, arrow (103) indicates that sample(101) is predicted from a sample or samples to the lower left of sample(101), in a 22.5 degree angle from the horizontal.

Still referring to FIG. 1A, on the top left there is depicted a squareblock (104) of 4×4 samples (indicated by a dashed, boldface line). Thesquare block (104) includes 16 samples, each labelled with an “S”, itsposition in the Y dimension (e.g., row index) and its position in the Xdimension (e.g., column index). For example, sample S21 is the secondsample in the Y dimension (from the top) and the first (from the left)sample in the X dimension. Similarly, sample S44 is the fourth sample inblock (104) in both the Y and X dimensions. As the block is 4×4 samplesin size, S44 is at the bottom right. Further shown are reference samplesthat follow a similar numbering scheme. A reference sample is labelledwith an R, its Y position (e.g., row index) and X position (columnindex) relative to block (104). In both H.264 and H.265, predictionsamples neighbor the block under reconstruction; therefore no negativevalues need to be used.

Intra picture prediction can work by copying reference sample valuesfrom the neighboring samples as appropriated by the signaled predictiondirection. For example, assume the coded video bitstream includessignaling that, for this block, indicates a prediction directionconsistent with arrow (102)—that is, samples are predicted from aprediction sample or samples to the upper right, at a 45 degree anglefrom the horizontal. In that case, samples S41, S32, S23, and S14 arepredicted from the same reference sample R05. Sample S44 is thenpredicted from reference sample R08.

In certain cases, the values of multiple reference samples may becombined, for example through interpolation, in order to calculate areference sample; especially when the directions are not evenlydivisible by 45 degrees.

The number of possible directions has increased as video codingtechnology has developed. In H.264 (year 2003), nine different directioncould be represented. That increased to 33 in H.265 (year 2013), andJEM/VVC/BMS, at the time of disclosure, can support up to 65 directions.Experiments have been conducted to identify the most likely directions,and certain techniques in the entropy coding are used to represent thoselikely directions in a small number of bits, accepting a certain penaltyfor less likely directions. Further, the directions themselves cansometimes be predicted from neighboring directions used in neighboring,already decoded, blocks.

FIG. 1B shows a schematic (110) that depicts 65 intra predictiondirections according to JEM to illustrate the increasing number ofprediction directions over time.

The mapping of intra prediction directions bits in the coded videobitstream that represent the direction can be different from videocoding technology to video coding technology; and can range, forexample, from simple direct mappings of prediction direction to intraprediction mode, to codewords, to complex adaptive schemes involvingmost probable modes, and similar techniques. In all cases, however,there can be certain directions that are statistically less likely tooccur in video content than certain other directions. As the goal ofvideo compression is the reduction of redundancy, those less likelydirections will, in a well working video coding technology, berepresented by a larger number of bits than more likely directions.

Motion compensation can be a lossy compression technique and can relateto techniques where a block of sample data from a previouslyreconstructed picture or part thereof (reference picture), after beingspatially shifted in a direction indicated by a motion vector (MVhenceforth), is used for the prediction of a newly reconstructed pictureor picture part. In some cases, the reference picture can be the same asthe picture currently under reconstruction. MVs can have two dimensionsX and Y, or three dimensions, the third being an indication of thereference picture in use (the latter, indirectly, can be a timedimension).

In some video compression techniques, an MV applicable to a certain areaof sample data can be predicted from other MVs, for example from thoserelated to another area of sample data spatially adjacent to the areaunder reconstruction, and preceding that MV in decoding order. Doing socan substantially reduce the amount of data required for coding the MV,thereby removing redundancy and increasing compression. MV predictioncan work effectively, for example, because when coding an input videosignal derived from a camera (known as natural video) there is astatistical likelihood that areas larger than the area to which a singleMV is applicable move in a similar direction and, therefore, can in somecases be predicted using a similar motion vector derived from MVs ofneighboring area. That results in the MV found for a given area to besimilar or the same as the MV predicted from the surrounding MVs, andthat in turn can be represented, after entropy coding, in a smallernumber of bits than what would be used if coding the MV directly. Insome cases, MV prediction can be an example of lossless compression of asignal (namely: the MVs) derived from the original signal (namely: thesample stream). In other cases, MV prediction itself can be lossy, forexample because of rounding errors when calculating a predictor fromseveral surrounding MVs.

Various MV prediction mechanisms are described in H.265/HEVC (ITU-T Rec.H.265, “High Efficiency Video Coding”, December 2016). Out of the manyMV prediction mechanisms that H.265 offers, described here is atechnique henceforth referred to as “spatial merge”.

Referring to FIG. 2 , a current block (201) comprises samples that havebeen found by the encoder during the motion search process to bepredictable from a previous block of the same size that has beenspatially shifted. Instead of coding that MV directly, the MV can bederived from metadata associated with one or more reference pictures,for example from the most recent (in decoding order) reference picture,using the MV associated with either one of five surrounding samples,denoted A0, A1, and B0, B1, B2 (202 through 206, respectively). InH.265, the MV prediction can use predictors from the same referencepicture that the neighboring block is using.

SUMMARY

Aspects of the disclosure provide methods and apparatuses for videoencoding and decoding. In some examples, an apparatus for video decodingincludes processing circuitry. The processing circuitry is configured toreceive a first supplemental enhancement information (SEI) messageincluding scalability dimension information (SDI). The first SEI messageincludes SDI of a plurality of views in a multiview bitstream. Themultiview bitstream includes a coded video sequence (CVS) with aplurality of layers. The processing circuitry can determine a value of afirst syntax element sdi_view_id_val[ ] in the first SEI message. Thefirst syntax element sdi_view_id_val[ ] indicates a view identifier(ViewId) of a layer in the plurality of layers. The processing circuitrycan determine, based on the first syntax element sdi_view_id_val[ ] inthe first SEI message, a target layer of the plurality of layers towhich a second syntax element of a second SEI message applies. A view ofthe plurality of views that is associated with the second syntax elementis indicated by the first syntax element sdi_view_id_val[ ].

In an embodiment, the first syntax element sdi_view_id_val[ ] in thefirst SEI message specifies the ViewId of the layer in the plurality oflayer. In an example, a view identifier of the view of the plurality ofviews that is associated with the second syntax element is equal to thevalue of the first syntax element sdi_view_id_val[ ].

In an embodiment, the second SEI message includes multiview acquisitioninformation (MAI). The second syntax element indicates view acquisitioninformation of the view of the plurality of views. The view acquisitioninformation includes an intrinsic camera parameter or an extrinsiccamera parameter that is used to acquire the view of the plurality ofviews.

In an embodiment, the second SEI message applies to a first access unitof the CVS.

In an embodiment, the second SEI message is not included in a scalablenesting SEI message.

In an embodiment, the second SEI message is included in the CVS based onthe first SEI message being included in the CVS. The processingcircuitry can determine the value of the first syntax elementsdi_view_id_val[ ] in the first SEI message and determine the targetlayer based on the first SEI message and the second SEI message beingincluded in the CVS.

In an embodiment, the first SEI message and the second SEI message applyto an access unit, and the first SEI message precedes the second SEImessage in a decoding order.

In an embodiment, a third SEI message indicating depth representationinformation is decoded, and the ViewId indicated by the first syntaxelement sdi_view_id_val[ ] is referenced by a third syntax element inthe third SEI message.

Aspects of the disclosure also provide a non-transitorycomputer-readable storage medium storing a program executable by atleast one processor to perform the methods for video decoding.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features, the nature, and various advantages of the disclosedsubject matter will be more apparent from the following detaileddescription and the accompanying drawings in which:

FIG. 1A is a schematic illustration of an exemplary subset of intraprediction modes.

FIG. 1B is an illustration of exemplary intra prediction directions.

FIG. 2 shows a current block (201) and surrounding samples in accordancewith an embodiment.

FIG. 3 is a schematic illustration of a simplified block diagram of acommunication system (300) in accordance with an embodiment.

FIG. 4 is a schematic illustration of a simplified block diagram of acommunication system (400) in accordance with an embodiment.

FIG. 5 is a schematic illustration of a simplified block diagram of adecoder in accordance with an embodiment.

FIG. 6 is a schematic illustration of a simplified block diagram of anencoder in accordance with an embodiment.

FIG. 7 shows a block diagram of an encoder in accordance with anotherembodiment.

FIG. 8 shows a block diagram of a decoder in accordance with anotherembodiment.

FIG. 9 shows a syntax example in a multiview acquisition information(MAI) supplemental enhancement information message that indicates MAIaccording to an embodiment of the disclosure.

FIG. 10 shows relationships between camera parameter variables andcorresponding syntax elements according to an embodiment of thedisclosure.

FIG. 11 shows a flow chart outlining an encoding process according to anembodiment of the disclosure.

FIG. 12 shows a flow chart outlining a decoding process according to anembodiment of the disclosure.

FIG. 13 is a schematic illustration of a computer system in accordancewith an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 3 illustrates a simplified block diagram of a communication system(300) according to an embodiment of the present disclosure. Thecommunication system (300) includes a plurality of terminal devices thatcan communicate with each other, via, for example, a network (350). Forexample, the communication system (300) includes a first pair ofterminal devices (310) and (320) interconnected via the network (350).In the FIG. 3 example, the first pair of terminal devices (310) and(320) performs unidirectional transmission of data. For example, theterminal device (310) may code video data (e.g., a stream of videopictures that are captured by the terminal device (310)) fortransmission to the other terminal device (320) via the network (350).The encoded video data can be transmitted in the form of one or morecoded video bitstreams. The terminal device (320) may receive the codedvideo data from the network (350), decode the coded video data torecover the video pictures and display video pictures according to therecovered video data. Unidirectional data transmission may be common inmedia serving applications and the like.

In another example, the communication system (300) includes a secondpair of terminal devices (330) and (340) that performs bidirectionaltransmission of coded video data that may occur, for example, duringvideoconferencing. For bidirectional transmission of data, in anexample, each terminal device of the terminal devices (330) and (340)may code video data (e.g., a stream of video pictures that are capturedby the terminal device) for transmission to the other terminal device ofthe terminal devices (330) and (340) via the network (350). Eachterminal device of the terminal devices (330) and (340) also may receivethe coded video data transmitted by the other terminal device of theterminal devices (330) and (340), and may decode the coded video data torecover the video pictures and may display video pictures at anaccessible display device according to the recovered video data.

In the FIG. 3 example, the terminal devices (310), (320), (330) and(340) may be illustrated as servers, personal computers and smart phonesbut the principles of the present disclosure may be not so limited.Embodiments of the present disclosure find application with laptopcomputers, tablet computers, media players and/or dedicated videoconferencing equipment. The network (350) represents any number ofnetworks that convey coded video data among the terminal devices (310),(320), (330) and (340), including for example wireline (wired) and/orwireless communication networks. The communication network (350) mayexchange data in circuit-switched and/or packet-switched channels.Representative networks include telecommunications networks, local areanetworks, wide area networks and/or the Internet. For the purposes ofthe present discussion, the architecture and topology of the network(350) may be immaterial to the operation of the present disclosureunless explained herein below.

FIG. 4 illustrates, as an example for an application for the disclosedsubject matter, the placement of a video encoder and a video decoder ina streaming environment. The disclosed subject matter can be equallyapplicable to other video enabled applications, including, for example,video conferencing, digital TV, storing of compressed video on digitalmedia including CD, DVD, memory stick and the like, and so on.

A streaming system may include a capture subsystem (413), that caninclude a video source (401), for example a digital camera, creating forexample a stream of video pictures (402) that are uncompressed. In anexample, the stream of video pictures (402) includes samples that aretaken by the digital camera. The stream of video pictures (402),depicted as a bold line to emphasize a high data volume when compared toencoded video data (404) (or coded video bitstreams), can be processedby an electronic device (420) that includes a video encoder (403)coupled to the video source (401). The video encoder (403) can includehardware, software, or a combination thereof to enable or implementaspects of the disclosed subject matter as described in more detailbelow. The encoded video data (404) (or encoded video bitstream),depicted as a thin line to emphasize the lower data volume when comparedto the stream of video pictures (402), can be stored on a streamingserver (405) for future use. One or more streaming client subsystems,such as client subsystems (406) and (408) in FIG. 4 can access thestreaming server (405) to retrieve copies (407) and (409) of the encodedvideo data (404). A client subsystem (406) can include a video decoder(410), for example, in an electronic device (430). The video decoder(410) decodes the incoming copy (407) of the encoded video data andcreates an outgoing stream of video pictures (411) that can be renderedon a display (412) (e.g., display screen) or other rendering device (notdepicted). In some streaming systems, the encoded video data (404),(407), and (409) (e.g., video bitstreams) can be encoded according tocertain video coding/compression standards. Examples of those standardsinclude ITU-T Recommendation H.265. In an example, a video codingstandard under development is informally known as Versatile Video Coding(VVC). The disclosed subject matter may be used in the context of VVC.

It is noted that the electronic devices (420) and (430) can includeother components (not shown). For example, the electronic device (420)can include a video decoder (not shown) and the electronic device (430)can include a video encoder (not shown) as well.

FIG. 5 shows a block diagram of a video decoder (510) according to anembodiment of the present disclosure. The video decoder (510) can beincluded in an electronic device (530). The electronic device (530) caninclude a receiver (531) (e.g., receiving circuitry). The video decoder(510) can be used in the place of the video decoder (410) in the FIG. 4example.

The receiver (531) may receive one or more coded video sequences to bedecoded by the video decoder (510); in the same or another embodiment,one coded video sequence at a time, where the decoding of each codedvideo sequence is independent from other coded video sequences. Thecoded video sequence may be received from a channel (501), which may bea hardware/software link to a storage device which stores the encodedvideo data. The receiver (531) may receive the encoded video data withother data, for example, coded audio data and/or ancillary data streams,that may be forwarded to their respective using entities (not depicted).The receiver (531) may separate the coded video sequence from the otherdata. To combat network jitter, a buffer memory (515) may be coupled inbetween the receiver (531) and an entropy decoder/parser (520) (“parser(520)” henceforth). In certain applications, the buffer memory (515) ispart of the video decoder (510). In others, it can be outside of thevideo decoder (510) (not depicted). In still others, there can be abuffer memory (not depicted) outside of the video decoder (510), forexample to combat network jitter, and in addition another buffer memory(515) inside the video decoder (510), for example to handle playouttiming. When the receiver (531) is receiving data from a store/forwarddevice of sufficient bandwidth and controllability, or from anisosynchronous network, the buffer memory (515) may not be needed, orcan be small. For use on best effort packet networks such as theInternet, the buffer memory (515) may be required, can be comparativelylarge and can be advantageously of adaptive size, and may at leastpartially be implemented in an operating system or similar elements (notdepicted) outside of the video decoder (510).

The video decoder (510) may include the parser (520) to reconstructsymbols (521) from the coded video sequence. Categories of those symbolsinclude information used to manage operation of the video decoder (510),and potentially information to control a rendering device such as arender device (512) (e.g., a display screen) that is not an integralpart of the electronic device (530) but can be coupled to the electronicdevice (530), as was shown in FIG. 5 . The control information for therendering device(s) may be in the form of Supplemental EnhancementInformation (SEI) messages or Video Usability Information (VUI)parameter set fragments (not depicted). The parser (520) mayparse/entropy-decode the coded video sequence that is received. Thecoding of the coded video sequence can be in accordance with a videocoding technology or standard, and can follow various principles,including variable length coding, Huffman coding, arithmetic coding withor without context sensitivity, and so forth. The parser (520) mayextract from the coded video sequence, a set of subgroup parameters forat least one of the subgroups of pixels in the video decoder, based uponat least one parameter corresponding to the group. Subgroups can includeGroups of Pictures (GOPs), pictures, tiles, slices, macroblocks, CodingUnits (CUs), blocks, Transform Units (TUs), Prediction Units (PUs) andso forth. The parser (520) may also extract from the coded videosequence information such as transform coefficients, quantizer parametervalues, motion vectors, and so forth.

The parser (520) may perform an entropy decoding/parsing operation onthe video sequence received from the buffer memory (515), so as tocreate symbols (521).

Reconstruction of the symbols (521) can involve multiple different unitsdepending on the type of the coded video picture or parts thereof (suchas: inter and intra picture, inter and intra block), and other factors.Which units are involved, and how, can be controlled by the subgroupcontrol information that was parsed from the coded video sequence by theparser (520). The flow of such subgroup control information between theparser (520) and the multiple units below is not depicted for clarity.

Beyond the functional blocks already mentioned, the video decoder (510)can be conceptually subdivided into a number of functional units asdescribed below. In a practical implementation operating undercommercial constraints, many of these units interact closely with eachother and can, at least partly, be integrated into each other. However,for the purpose of describing the disclosed subject matter, theconceptual subdivision into the functional units below is appropriate.

A first unit is the scaler/inverse transform unit (551). Thescaler/inverse transform unit (551) receives a quantized transformcoefficient as well as control information, including which transform touse, block size, quantization factor, quantization scaling matrices,etc. as symbol(s) (521) from the parser (520). The scaler/inversetransform unit (551) can output blocks comprising sample values, thatcan be input into aggregator (555).

In some cases, the output samples of the scaler/inverse transform unit(551) can pertain to an intra coded block; that is: a block that is notusing predictive information from previously reconstructed pictures, butcan use predictive information from previously reconstructed parts ofthe current picture. Such predictive information can be provided by anintra picture prediction unit (552). In some cases, the intra pictureprediction unit (552) generates a block of the same size and shape ofthe block under reconstruction, using surrounding already reconstructedinformation fetched from the current picture buffer (558). The currentpicture buffer (558) buffers, for example, partly reconstructed currentpicture and/or fully reconstructed current picture. The aggregator(555), in some cases, adds, on a per sample basis, the predictioninformation the intra prediction unit (552) has generated to the outputsample information as provided by the scaler/inverse transform unit(551).

In other cases, the output samples of the scaler/inverse transform unit(551) can pertain to an inter coded, and potentially motion compensatedblock. In such a case, a motion compensation prediction unit (553) canaccess reference picture memory (557) to fetch samples used forprediction. After motion compensating the fetched samples in accordancewith the symbols (521) pertaining to the block, these samples can beadded by the aggregator (555) to the output of the scaler/inversetransform unit (551) (in this case called the residual samples orresidual signal) so as to generate output sample information. Theaddresses within the reference picture memory (557) from where themotion compensation prediction unit (553) fetches prediction samples canbe controlled by motion vectors, available to the motion compensationprediction unit (553) in the form of symbols (521) that can have, forexample X, Y, and reference picture components. Motion compensation alsocan include interpolation of sample values as fetched from the referencepicture memory (557) when sub-sample exact motion vectors are in use,motion vector prediction mechanisms, and so forth.

The output samples of the aggregator (555) can be subject to variousloop filtering techniques in the loop filter unit (556). Videocompression technologies can include in-loop filter technologies thatare controlled by parameters included in the coded video sequence (alsoreferred to as coded video bitstream) and made available to the loopfilter unit (556) as symbols (521) from the parser (520), but can alsobe responsive to meta-information obtained during the decoding ofprevious (in decoding order) parts of the coded picture or coded videosequence, as well as responsive to previously reconstructed andloop-filtered sample values.

The output of the loop filter unit (556) can be a sample stream that canbe output to the render device (512) as well as stored in the referencepicture memory (557) for use in future inter-picture prediction.

Certain coded pictures, once fully reconstructed, can be used asreference pictures for future prediction. For example, once a codedpicture corresponding to a current picture is fully reconstructed andthe coded picture has been identified as a reference picture (by, forexample, the parser (520)), the current picture buffer (558) can becomea part of the reference picture memory (557), and a fresh currentpicture buffer can be reallocated before commencing the reconstructionof the following coded picture.

The video decoder (510) may perform decoding operations according to apredetermined video compression technology in a standard, such as ITU-TRec. H.265. The coded video sequence may conform to a syntax specifiedby the video compression technology or standard being used, in the sensethat the coded video sequence adheres to both the syntax of the videocompression technology or standard and the profiles as documented in thevideo compression technology or standard. Specifically, a profile canselect certain tools as the only tools available for use under thatprofile from all the tools available in the video compression technologyor standard. Also necessary for compliance can be that the complexity ofthe coded video sequence is within bounds as defined by the level of thevideo compression technology or standard. In some cases, levels restrictthe maximum picture size, maximum frame rate, maximum reconstructionsample rate (measured in, for example megasamples per second), maximumreference picture size, and so on. Limits set by levels can, in somecases, be further restricted through Hypothetical Reference Decoder(HRD) specifications and metadata for HRD buffer management signaled inthe coded video sequence.

In an embodiment, the receiver (531) may receive additional (redundant)data with the encoded video. The additional data may be included as partof the coded video sequence(s). The additional data may be used by thevideo decoder (510) to properly decode the data and/or to moreaccurately reconstruct the original video data. Additional data can bein the form of, for example, temporal, spatial, or signal noise ratio(SNR) enhancement layers, redundant slices, redundant pictures, forwarderror correction codes, and so on.

FIG. 6 shows a block diagram of a video encoder (603) according to anembodiment of the present disclosure. The video encoder (603) isincluded in an electronic device (620). The electronic device (620)includes a transmitter (640) (e.g., transmitting circuitry). The videoencoder (603) can be used in the place of the video encoder (403) in theFIG. 4 example.

The video encoder (603) may receive video samples from a video source(601) (that is not part of the electronic device (620) in the FIG. 6example) that may capture video image(s) to be coded by the videoencoder (603). In another example, the video source (601) is a part ofthe electronic device (620).

The video source (601) may provide the source video sequence to be codedby the video encoder (603) in the form of a digital video sample streamthat can be of any suitable bit depth (for example: 8 bit, 10 bit, 12bit, . . . ), any colorspace (for example, BT.601 Y CrCB, RGB, . . . ),and any suitable sampling structure (for example Y CrCb 4:2:0, Y CrCb4:4:4). In a media serving system, the video source (601) may be astorage device storing previously prepared video. In a videoconferencingsystem, the video source (601) may be a camera that captures local imageinformation as a video sequence. Video data may be provided as aplurality of individual pictures that impart motion when viewed insequence. The pictures themselves may be organized as a spatial array ofpixels, wherein each pixel can comprise one or more samples depending onthe sampling structure, color space, etc. in use. A person skilled inthe art can readily understand the relationship between pixels andsamples. The description below focuses on samples.

According to an embodiment, the video encoder (603) may code andcompress the pictures of the source video sequence into a coded videosequence (643) in real time or under any other time constraints asrequired by the application. Enforcing appropriate coding speed is onefunction of a controller (650). In some embodiments, the controller(650) controls other functional units as described below and isfunctionally coupled to the other functional units. The coupling is notdepicted for clarity. Parameters set by the controller (650) can includerate control related parameters (picture skip, quantizer, lambda valueof rate-distortion optimization techniques, . . . ), picture size, groupof pictures (GOP) layout, maximum motion vector search range, and soforth. The controller (650) can be configured to have other suitablefunctions that pertain to the video encoder (603) optimized for acertain system design.

In some embodiments, the video encoder (603) is configured to operate ina coding loop. As an oversimplified description, in an example, thecoding loop can include a source coder (630) (e.g., responsible forcreating symbols, such as a symbol stream, based on an input picture tobe coded, and a reference picture(s)), and a (local) decoder (633)embedded in the video encoder (603). The decoder (633) reconstructs thesymbols to create the sample data in a similar manner as a (remote)decoder also would create (as any compression between symbols and codedvideo bitstream is lossless in the video compression technologiesconsidered in the disclosed subject matter). The reconstructed samplestream (sample data) is input to the reference picture memory (634). Asthe decoding of a symbol stream leads to bit-exact results independentof decoder location (local or remote), the content in the referencepicture memory (634) is also bit exact between the local encoder andremote encoder. In other words, the prediction part of an encoder “sees”as reference picture samples exactly the same sample values as a decoderwould “see” when using prediction during decoding. This fundamentalprinciple of reference picture synchronicity (and resulting drift, ifsynchronicity cannot be maintained, for example because of channelerrors) is used in some related arts as well.

The operation of the “local” decoder (633) can be the same as of a“remote” decoder, such as the video decoder (510), which has alreadybeen described in detail above in conjunction with FIG. 5 . Brieflyreferring also to FIG. 5 , however, as symbols are available andencoding/decoding of symbols to a coded video sequence by an entropycoder (645) and the parser (520) can be lossless, the entropy decodingparts of the video decoder (510), including the buffer memory (515), andparser (520) may not be fully implemented in the local decoder (633).

In an embodiment, a decoder technology except the parsing/entropydecoding that is present in a decoder is present, in an identical or asubstantially identical functional form, in a corresponding encoder.Accordingly, the disclosed subject matter focuses on decoder operation.The description of encoder technologies can be abbreviated as they arethe inverse of the comprehensively described decoder technologies. Incertain areas a more detail description is provided below.

During operation, in some examples, the source coder (630) may performmotion compensated predictive coding, which codes an input picturepredictively with reference to one or more previously coded picture fromthe video sequence that were designated as “reference pictures.” In thismanner, the coding engine (632) codes differences between pixel blocksof an input picture and pixel blocks of reference picture(s) that may beselected as prediction reference(s) to the input picture.

The local video decoder (633) may decode coded video data of picturesthat may be designated as reference pictures, based on symbols createdby the source coder (630). Operations of the coding engine (632) mayadvantageously be lossy processes. When the coded video data may bedecoded at a video decoder (not shown in FIG. 6 ), the reconstructedvideo sequence typically may be a replica of the source video sequencewith some errors. The local video decoder (633) replicates decodingprocesses that may be performed by the video decoder on referencepictures and may cause reconstructed reference pictures to be stored inthe reference picture memory (634). In this manner, the video encoder(603) may store copies of reconstructed reference pictures locally thathave common content as the reconstructed reference pictures that will beobtained by a far-end video decoder (absent transmission errors).

The predictor (635) may perform prediction searches for the codingengine (632). That is, for a new picture to be coded, the predictor(635) may search the reference picture memory (634) for sample data (ascandidate reference pixel blocks) or certain metadata such as referencepicture motion vectors, block shapes, and so on, that may serve as anappropriate prediction reference for the new pictures. The predictor(635) may operate on a sample block-by-pixel block basis to findappropriate prediction references. In some cases, as determined bysearch results obtained by the predictor (635), an input picture mayhave prediction references drawn from multiple reference pictures storedin the reference picture memory (634).

The controller (650) may manage coding operations of the source coder(630), including, for example, setting of parameters and subgroupparameters used for encoding the video data.

Output of all aforementioned functional units may be subjected toentropy coding in the entropy coder (645). The entropy coder (645)translates the symbols as generated by the various functional units intoa coded video sequence, by lossless compressing the symbols according totechnologies such as Huffman coding, variable length coding, arithmeticcoding, and so forth.

The transmitter (640) may buffer the coded video sequence(s) as createdby the entropy coder (645) to prepare for transmission via acommunication channel (660), which may be a hardware/software link to astorage device which would store the encoded video data. The transmitter(640) may merge coded video data from the video encoder (603) with otherdata to be transmitted, for example, coded audio data and/or ancillarydata streams (sources not shown).

The controller (650) may manage operation of the video encoder (603).During coding, the controller (650) may assign to each coded picture acertain coded picture type, which may affect the coding techniques thatmay be applied to the respective picture. For example, pictures oftenmay be assigned as one of the following picture types:

An Intra Picture (I picture) may be one that may be coded and decodedwithout using any other picture in the sequence as a source ofprediction. Some video codecs allow for different types of intrapictures, including, for example Independent Decoder Refresh (“IDR”)Pictures. A person skilled in the art is aware of those variants of Ipictures and their respective applications and features.

A predictive picture (P picture) may be one that may be coded anddecoded using intra prediction or inter prediction using at most onemotion vector and reference index to predict the sample values of eachblock.

A bi-directionally predictive picture (B Picture) may be one that may becoded and decoded using intra prediction or inter prediction using atmost two motion vectors and reference indices to predict the samplevalues of each block. Similarly, multiple-predictive pictures can usemore than two reference pictures and associated metadata for thereconstruction of a single block.

Source pictures commonly may be subdivided spatially into a plurality ofsample blocks (for example, blocks of 4×4, 8×8, 4×8, or 16×16 sampleseach) and coded on a block-by-block basis. Blocks may be codedpredictively with reference to other (already coded) blocks asdetermined by the coding assignment applied to the blocks' respectivepictures. For example, blocks of I pictures may be codednon-predictively or they may be coded predictively with reference toalready coded blocks of the same picture (spatial prediction or intraprediction). Pixel blocks of P pictures may be coded predictively, viaspatial prediction or via temporal prediction with reference to onepreviously coded reference picture. Blocks of B pictures may be codedpredictively, via spatial prediction or via temporal prediction withreference to one or two previously coded reference pictures.

The video encoder (603) may perform coding operations according to apredetermined video coding technology or standard, such as ITU-T Rec.H.265. In its operation, the video encoder (603) may perform variouscompression operations, including predictive coding operations thatexploit temporal and spatial redundancies in the input video sequence.The coded video data, therefore, may conform to a syntax specified bythe video coding technology or standard being used.

In an embodiment, the transmitter (640) may transmit additional datawith the encoded video. The source coder (630) may include such data aspart of the coded video sequence. Additional data may comprisetemporal/spatial/SNR enhancement layers, other forms of redundant datasuch as redundant pictures and slices, SEI messages, VUI parameter setfragments, and so on.

A video may be captured as a plurality of source pictures (videopictures) in a temporal sequence. Intra-picture prediction (oftenabbreviated to intra prediction) makes use of spatial correlation in agiven picture, and inter-picture prediction makes uses of the (temporalor other) correlation between the pictures. In an example, a specificpicture under encoding/decoding, which is referred to as a currentpicture, is partitioned into blocks. When a block in the current pictureis similar to a reference block in a previously coded and still bufferedreference picture in the video, the block in the current picture can becoded by a vector that is referred to as a motion vector. The motionvector points to the reference block in the reference picture, and canhave a third dimension identifying the reference picture, in casemultiple reference pictures are in use.

In some embodiments, a bi-prediction technique can be used in theinter-picture prediction. According to the bi-prediction technique, tworeference pictures, such as a first reference picture and a secondreference picture that are both prior in decoding order to the currentpicture in the video (but may be in the past and future, respectively,in display order) are used. A block in the current picture can be codedby a first motion vector that points to a first reference block in thefirst reference picture, and a second motion vector that points to asecond reference block in the second reference picture. The block can bepredicted by a combination of the first reference block and the secondreference block.

Further, a merge mode technique can be used in the inter-pictureprediction to improve coding efficiency.

According to some embodiments of the disclosure, predictions, such asinter-picture predictions and intra-picture predictions are performed inthe unit of blocks. For example, according to the HEVC standard, apicture in a sequence of video pictures is partitioned into coding treeunits (CTU) for compression, the CTUs in a picture have the same size,such as 64×64 pixels, 32×32 pixels, or 16×16 pixels. In general, a CTUincludes three coding tree blocks (CTBs), which are one luma CTB and twochroma CTBs. Each CTU can be recursively quadtree split into one ormultiple coding units (CUs). For example, a CTU of 64×64 pixels can besplit into one CU of 64×64 pixels, or 4 CUs of 32×32 pixels, or 16 CUsof 16×16 pixels. In an example, each CU is analyzed to determine aprediction type for the CU, such as an inter prediction type or an intraprediction type. The CU is split into one or more prediction units (PUs)depending on the temporal and/or spatial predictability. Generally, eachPU includes a luma prediction block (PB), and two chroma PBs. In anembodiment, a prediction operation in coding (encoding/decoding) isperformed in the unit of a prediction block. Using a luma predictionblock as an example of a prediction block, the prediction block includesa matrix of values (e.g., luma values) for pixels, such as 8×8 pixels,16×16 pixels, 8×16 pixels, 16×8 pixels, and the like.

FIG. 7 shows a diagram of a video encoder (703) according to anotherembodiment of the disclosure. The video encoder (703) is configured toreceive a processing block (e.g., a prediction block) of sample valueswithin a current video picture in a sequence of video pictures, andencode the processing block into a coded picture that is part of a codedvideo sequence. In an example, the video encoder (703) is used in theplace of the video encoder (403) in the FIG. 4 example.

In an HEVC example, the video encoder (703) receives a matrix of samplevalues for a processing block, such as a prediction block of 8×8samples, and the like. The video encoder (703) determines whether theprocessing block is best coded using intra mode, inter mode, orbi-prediction mode using, for example, rate-distortion optimization.When the processing block is to be coded in intra mode, the videoencoder (703) may use an intra prediction technique to encode theprocessing block into the coded picture; and when the processing blockis to be coded in inter mode or bi-prediction mode, the video encoder(703) may use an inter prediction or bi-prediction technique,respectively, to encode the processing block into the coded picture. Incertain video coding technologies, merge mode can be an inter pictureprediction submode where the motion vector is derived from one or moremotion vector predictors without the benefit of a coded motion vectorcomponent outside the predictors. In certain other video codingtechnologies, a motion vector component applicable to the subject blockmay be present. In an example, the video encoder (703) includes othercomponents, such as a mode decision module (not shown) to determine themode of the processing blocks.

In the FIG. 7 example, the video encoder (703) includes the interencoder (730), an intra encoder (722), a residue calculator (723), aswitch (726), a residue encoder (724), a general controller (721), andan entropy encoder (725) coupled together as shown in FIG. 7 .

The inter encoder (730) is configured to receive the samples of thecurrent block (e.g., a processing block), compare the block to one ormore reference blocks in reference pictures (e.g., blocks in previouspictures and later pictures), generate inter prediction information(e.g., description of redundant information according to inter encodingtechnique, motion vectors, merge mode information), and calculate interprediction results (e.g., predicted block) based on the inter predictioninformation using any suitable technique. In some examples, thereference pictures are decoded reference pictures that are decoded basedon the encoded video information.

The intra encoder (722) is configured to receive the samples of thecurrent block (e.g., a processing block), in some cases compare theblock to blocks already coded in the same picture, generate quantizedcoefficients after transform, and in some cases also intra predictioninformation (e.g., an intra prediction direction information accordingto one or more intra encoding techniques). In an example, the intraencoder (722) also calculates intra prediction results (e.g., predictedblock) based on the intra prediction information and reference blocks inthe same picture.

The general controller (721) is configured to determine general controldata and control other components of the video encoder (703) based onthe general control data. In an example, the general controller (721)determines the mode of the block, and provides a control signal to theswitch (726) based on the mode. For example, when the mode is the intramode, the general controller (721) controls the switch (726) to selectthe intra mode result for use by the residue calculator (723), andcontrols the entropy encoder (725) to select the intra predictioninformation and include the intra prediction information in thebitstream; and when the mode is the inter mode, the general controller(721) controls the switch (726) to select the inter prediction resultfor use by the residue calculator (723), and controls the entropyencoder (725) to select the inter prediction information and include theinter prediction information in the bitstream.

The residue calculator (723) is configured to calculate a difference(residue data) between the received block and prediction resultsselected from the intra encoder (722) or the inter encoder (730). Theresidue encoder (724) is configured to operate based on the residue datato encode the residue data to generate the transform coefficients. In anexample, the residue encoder (724) is configured to convert the residuedata from a spatial domain to a frequency domain, and generate thetransform coefficients. The transform coefficients are then subject toquantization processing to obtain quantized transform coefficients. Invarious embodiments, the video encoder (703) also includes a residuedecoder (728). The residue decoder (728) is configured to performinverse-transform, and generate the decoded residue data. The decodedresidue data can be suitably used by the intra encoder (722) and theinter encoder (730). For example, the inter encoder (730) can generatedecoded blocks based on the decoded residue data and inter predictioninformation, and the intra encoder (722) can generate decoded blocksbased on the decoded residue data and the intra prediction information.The decoded blocks are suitably processed to generate decoded picturesand the decoded pictures can be buffered in a memory circuit (not shown)and used as reference pictures in some examples.

The entropy encoder (725) is configured to format the bitstream toinclude the encoded block. The entropy encoder (725) is configured toinclude various information according to a suitable standard, such asthe HEVC standard. In an example, the entropy encoder (725) isconfigured to include the general control data, the selected predictioninformation (e.g., intra prediction information or inter predictioninformation), the residue information, and other suitable information inthe bitstream. Note that, according to the disclosed subject matter,when coding a block in the merge submode of either inter mode orbi-prediction mode, there is no residue information.

FIG. 8 shows a diagram of a video decoder (810) according to anotherembodiment of the disclosure. The video decoder (810) is configured toreceive coded pictures that are part of a coded video sequence, anddecode the coded pictures to generate reconstructed pictures. In anexample, the video decoder (810) is used in the place of the videodecoder (410) in the FIG. 4 example.

In the FIG. 8 example, the video decoder (810) includes an entropydecoder (871), an inter decoder (880), a residue decoder (873), areconstruction module (874), and an intra decoder (872) coupled togetheras shown in FIG. 8 .

The entropy decoder (871) can be configured to reconstruct, from thecoded picture, certain symbols that represent the syntax elements ofwhich the coded picture is made up. Such symbols can include, forexample, the mode in which a block is coded (such as, for example, intramode, inter mode, bi-predicted mode, the latter two in merge submode oranother submode), prediction information (such as, for example, intraprediction information or inter prediction information) that canidentify certain sample or metadata that is used for prediction by theintra decoder (872) or the inter decoder (880), respectively, residualinformation in the form of, for example, quantized transformcoefficients, and the like. In an example, when the prediction mode isinter or bi-predicted mode, the inter prediction information is providedto the inter decoder (880); and when the prediction type is the intraprediction type, the intra prediction information is provided to theintra decoder (872). The residual information can be subject to inversequantization and is provided to the residue decoder (873).

The inter decoder (880) is configured to receive the inter predictioninformation, and generate inter prediction results based on the interprediction information.

The intra decoder (872) is configured to receive the intra predictioninformation, and generate prediction results based on the intraprediction information.

The residue decoder (873) is configured to perform inverse quantizationto extract de-quantized transform coefficients, and process thede-quantized transform coefficients to convert the residual from thefrequency domain to the spatial domain. The residue decoder (873) mayalso require certain control information (to include the QuantizerParameter (QP)), and that information may be provided by the entropydecoder (871) (data path not depicted as this may be low volume controlinformation only).

The reconstruction module (874) is configured to combine, in the spatialdomain, the residual as output by the residue decoder (873) and theprediction results (as output by the inter or intra prediction modulesas the case may be) to form a reconstructed block, that may be part ofthe reconstructed picture, which in turn may be part of thereconstructed video. It is noted that other suitable operations, such asa deblocking operation and the like, can be performed to improve thevisual quality.

It is noted that the video encoders (403), (603), and (703), and thevideo decoders (410), (510), and (810) can be implemented using anysuitable technique. In an embodiment, the video encoders (403), (603),and (703), and the video decoders (410), (510), and (810) can beimplemented using one or more integrated circuits. In anotherembodiment, the video encoders (403), (603), and (603), and the videodecoders (410), (510), and (810) can be implemented using one or moreprocessors that execute software instructions.

According to an embodiment of the disclosure, a bitstream can includeone or more coded video sequences (CVSs). A CVS can be independentlycoded from other CVSs. Each CVS can include one or more layers, and eachlayer can be a representation of a video with a specific quality (e.g.,a spatial resolution), or a representation of a certain componentinterpretation property, e.g., as a depth map, a transparency map, or aperspective view. In a temporal dimension, each CVS can include one ormore access units (AUs). Each AU can include one or more pictures ofdifferent layers that correspond to a same time instance. A coded layervideo sequence (CLVS) is a layer-wise CVS that can include a sequence ofpicture units in the same layer. If a bitstream has multiple layers, aCVS in the bitstream can have one or more CLVSs for each layer.

In an embodiment, a CVS includes a sequence of AUs where the sequence ofAUs includes, in a decoding order, an intra random access point (IRAP)AU, followed by zero or more AUs that are not IRAP AUs. In an example,the zero or more AUs includes all subsequent AUs up to but not includingany subsequent AU that is an IRAP AU. In an example, a CLVS includes asequence of pictures and the associated non-video coding layer (VCL)network abstraction layer (NAL) units of a base layer of a CVS.

According to some aspects of the disclosure, video can be categorizedinto single view videos and multiview videos. For example, a single viewvideo (e.g., a monoscopic video) is a two-dimensional medium thatprovides viewers a single view of a scene. A multiview video can providemultiple viewpoints of a scene, and can provide viewers the sensation ofrealism. In an example, a 3D video can provide two views, such as a leftview and a right view corresponding to a human viewer. The two views maybe displayed (presented) simultaneously or near simultaneously usingdifferent polarizations of light, and a viewer may wear polarizedglasses such that each of the viewer's eyes receives a respective one ofthe views. In an example, the left view and the right view are acquiredby two different cameras located at different positions.

A multiview video can be created by capturing a scene using multiplecameras simultaneously, where the multiple cameras are properly locatedso that each camera captures the scene from one viewpoint. The multiplecameras can capture multiple video sequences corresponding to multipleviewpoints. To provide more views, more cameras can be used to generatea multiview video with a large number of video sequences associated withthe views. The multi-view video may require a large storage space tostore and/or a high bandwidth to transmit. Multiview video codingtechniques have been developed in the field to reduce the requiredstorage space or the transmission bandwidth.

To improve efficiency of multiview video coding, the similaritiesbetween views are exploited. In some embodiments, one of the views thatis referred to as a base view, is encoded like a monoscopic video. Forexample, during the encoding of the base view, the intra(picture) and/ortemporal inter(picture) predictions are used. The base view may bedecoded using a monoscopic decoder (e.g., a monoscopic decoder) thatperforms intra(picture) prediction and the inter(picture) prediction.Other views beside the base view in the multiview video can be referredto as dependent views. To code the dependent views, in addition tointra(picture) and inter(picture) predictions, the inter-view predictionwith disparity compensation may be used. In an example, in an inter-viewprediction, a current block in a dependent view is predicted using areference block of samples from a picture of another view in the sametime instance. The location of the reference block is indicated out by adisparity vector. The inter-view prediction is similar to theinter(picture) prediction except that the motion vectors are replaced bythe disparity vectors, and the temporal reference pictures are replacedby the reference pictures from other views.

According to some aspects of the disclosure, multiview coding can employa multi-layer approach. The multi-layer approach can multiplex differentcoded (e.g., HEVC-coded) representations of video sequences, calledlayers, into one bitstream. The layers can depend on each other.Dependencies can be used by inter-layer prediction to achieve increasedcompression performance by exploiting similarities among differentlayers. A layer can represent texture, depth or other auxiliaryinformation of a scene related to a particular camera perspective. Insome examples, all layers belonging to the same camera perspective aredenoted as a view; and layers carrying the same type of information(e.g., texture or depth) are called components in the scope of multiviewvideo.

A multiview bitstream can include one or more CVSs. A CVS can includemultiple views of a scene. The multiple views of the scene can beacquired, for example, from different viewpoints by respective cameras.Data (e.g., texture, depth or other auxiliary information) of each viewcan be included in one or more layers in the CVS.

According to an aspect of the disclosure, the multiview video coding caninclude high level syntax (HLS) (e.g., higher than a slice level)additions with existing single layer decoding cores. In some examples,the multiview view coding does not change the syntax or decoding processrequired for (e.g., HEVC) single-layer coding below the slice level.Re-use of existing implementations without major changes for buildingmultiview video decoders can be allowed. For example, a multiview videodecoder can be implemented based on the video decoder (510) or the videodecoder (810).

In some examples, all pictures associated with the same capturing ordisplay time instance are contained in an AU and have the same pictureorder count (POC). The multiview video coding can allow inter-viewprediction that performs prediction from pictures in the same AU. Forexample, the decoded pictures from other views can be inserted into oneor both of the reference picture lists of a current picture. Further, insome examples, the motion vectors may be actual temporal motion vectorswhen related to temporal reference pictures of the same view, or may bedisparity vectors when related to inter-view reference pictures.Block-level motion compensation modules (e.g., block level encodingsoftware or hardware, block level decoding software or hardware) can beused which operate the same way regardless of whether a motion vector isa temporal motion vector or a disparity vector.

According to some aspects of the disclosure, supplemental enhancementinformation (SEI) messages can be included in an encoded bitstream, forexample, to assist in the decoding and/or display of the encodedbitstream, or for another purpose. SEI message(s) can includeinformation that is not necessary for decoding, such as decoding samplesof coded pictures from VCL NAL units. SEI message(s) can be optional forconstructing luma or chroma samples by a decoding process. In someexamples, SEI messages is not required for reconstructing luma or chromasamples during the decoding process. Additionally, decoders that conformto a video coding standard that supports SEI messages are not requiredto process SEI messages to be conforming. For some coding standards,some SEI message information may be required to check bitstreamconformance or for outputting timing decoder conformance. SEI message(s)may be optionally processed by conforming decoders for output orderconformance to a certain standard (e.g., HEVC 265 or VVC). In anembodiment, SEI message(s) are present (e.g., signaled) in thebitstream.

SEI messages can contain various types of data that indicate the timingof the video pictures or describe various properties of the coded videoor how the various properties can be used or enhanced. In some examples,SEI messages do not affect the core decoding process, but can indicatehow the video is recommended to be post-processed or displayed.

SEI messages can be used to provide additional information about anencoded bitstream, which can be used to change the presentation of thebitstream when the bitstream is decoded, or to provide information to adecoder. For example, SEI messages have been used to provide framepacking information (e.g., describing the manner in which video data isarranged in a video frame), content descriptions (e.g., to indicate thatthe encoded bitstream is, for example, 360-degree video), and colorinformation (e.g., color gamut and/or color range), among other things.

In some examples, an SEI message can be used to signal to a decoder thatthe encoded bitstream includes 360-degree video or a VR video. Thedecoder can use the above information to render the video data for a360-degree presentation. Alternatively, if the decoder is not capable ofrendering 360-degree video, the decoder can use the above information tonot render the video data.

The disclosure includes multiview-related information. The multi-viewrelated information can be included in multiview-related SEI messages ina coded video stream, such as a scalability dimension information (SDI)SEI message and a multiview acquisition information (MAI) SEI message.In an example, a variable ViewId (e.g., ViewId associated with a viewidentifier of an i-th layer in a CVS) in the semantics of a first SEImessage (e.g., the SDI SEI message) is defined. In an example, a targetlayer to which a second SEI message (e.g., the MAI or depthrepresentation information SEI message) is applied is clarified.

According to an embodiment of the disclosure, a first SEI message or anSDI SEI message can indicate scalability dimension information (SDI),for example, of a multiview video. A CVS in a bitstream (e.g., amultiview bitstream) can include a sequence of AUs that includes, in adecoding order, an AU containing an SDI SEI message, followed by zero ormore AUs, including all subsequent AUs up to but not including anysubsequent AU that includes an SDI SEI message. When an SDI SEI messageis present in an AU of a CVS, the SDI SEI message can be present for thefirst AU of the CVS. In an example, all SDI SEI messages that apply tothe same CVS can have the same content. In an example, an SDI SEImessage cannot be included in a scalable nesting SEI message.

Table 1 shows an example of a syntax of an SDI SEI message according toan embodiment of the disclosure.

TABLE 1 Scalability dimension information (SDI) SEI message syntaxDescriptor scalability_dimension_info( payloadSize ) { sdi_max_layers_minus1 u(6)  sdi_multiview_info_flag u(1) sdi_auxiliary_info_flag u(1)  if( sdi_multiview_info_flag | |sdi_auxiliary_info_flag ) {   if( sdi_multiview_info_flag )   sdi_view_id_len_minus1 u(4)   for( i = 0; i <= sdi_max_layers_minus1;i++ ) {    if( sdi_multiview_info_flag )     sdi_view_id_val[ i ] u(v)   if( sdi_auxiliary_info_flag )     sdi_aux_id[ i ] u(8)   }  } }

The first SEI message (e.g., the SDI SEI message) may include a numberand types of scalability dimensions, such as information indicating thenumber of views and the like for the multiview video. The first SEImessage can include the SDI for each layer in a CVS of a bitstream. Inan example, the bitstream is a multiview bitstream, the SDI indicates aview identifier (ID) (e.g., the variable ViewID) of each layer, forexample, using a syntax element sdi_view_id_val[i]. In an example,auxiliary information, such as depth or alpha, is included in one ormore layers in the bitstream, and an auxiliary ID of each layer isindicated in the first SEI message.

The syntax element sdi_max_layers_minus1 plus 1 can indicate a maximumnumber of layers in the bitstream or the CVS.

The syntax element sdi_multiview_info_flag equal to 1 can indicate thatthe bitstream may be a multiview bitstream and the sdi_view_id_val[ ]syntax elements are present in the SDI SEI message. The syntax elementsdi_multiview_flag equal to 0 can indicate that the bitstream is not amultiview bitstream and the sdi_view_id_val[ ] syntax elements are notpresent in the SDI SEI message.

The syntax element sdi_auxiliary_info_flag equal to 1 can indicate thatauxiliary information can be carried by one or more layers in thebitstream or the CVS and the sdi_aux_id[ ] syntax elements are presentin the SDI SEI message. The syntax element sdi_auxiliary_info_flag equalto 0 can indicate that no auxiliary information is carried by one ormore layers in the bitstream or the CVS and the sdi_aux_id[ ] syntaxelements are not present in the SDI SEI message.

The syntax element sdi_aux_id[i] equal to 0 can indicate that the i-thlayer in the bitstream or the CVS does not include auxiliary pictures.The syntax element sdi_aux_id[i] greater than 0 can indicate the type ofauxiliary pictures in the i-th layer in the bitstream or the CVSaccording to Table 2. When the sdi_auxiliary_info_flag is equal to 0,the value of sdi_aux_id[i] is inferred to be equal to 0.

TABLE 2 Mapping of sdi_aux_id[i] to the type of auxiliary picturessdi_aux_id[ i ] Name Type of auxiliary pictures 1 AUX_ALPHA Alpha plane2 AUX_DEPTH Depth picture  3 . . . 127 Reserved 128 . . . 159Unspecified 160 . . . 255 Reserved

The interpretation of auxiliary pictures associated with sdi_aux_id inthe range of 128 to 159, inclusive, can be specified through means otherthan the sdi_aux_id value.

The syntax element sdi_aux_id[i] can be in the range of 0 to 2,inclusive, or 128 to 159, inclusive, for bitstreams conforming to aversion shown in Table 2. In some embodiments, decoders can allow valuesof sdi_aux_id[i] in the range of 0 to 255, inclusive.

In certain video coding technologies, such as versatile supplementalenhancement information (VSEI), the variable ViewId is not defined, butis referred to by certain semantics.

According to an embodiment of the disclosure, the variable ViewID (e.g.,ViewId of an i-th layer in a current CVS) can be defined or specified inthe first SEI message (e.g., the SDI SEI message). In an example, thesyntax element sdi_view_id_val[i] in the first SEI message (e.g., theSDI SEI message) specifies a value of the variable ViewID of the i-thlayer in the current CVS (e.g., the current CVS in the bitstream). Thesyntax element sdi_view_id_val[i] can be signaled in the first SEImessage (e.g., the SDI SEI message).

In an example, different layers in the current CVS correspond todifferent views, and values of the variable ViewID of different layersin the current CVS are different. In an example, multiple layers in thecurrent CVS correspond to a same view, and values of the variable ViewIDof the multiple layers in the current CVS are identical. For example,sdi_view_id_val[i1] is equal to sdi_view_id_val[i2] where i1 isdifferent from i2.

In an example, a multiview bitstream includes a CVS that has two layers(e.g., layer 0 and layer 1). The multiview bitstream includes two views,e.g., view 0 and view 1 that correspond to the layer 0 and layer 1,respectively. The syntax element sdi_view_id_val[ ] has two values,e.g., sdi_view_id_val[0 (layer 0)]=0 (view 0), and sdi_view_id_val[1(layer 1)]=1 (view 1).

In an example, a multiview bitstream includes a CVS that has four layers(e.g., layers 0-3). The multiview bitstream includes the two views,e.g., view 0 and view 1. View 0 corresponds to the layer 0 and layer 1.View 1 corresponds to the layer 2 and layer 3. The syntax elementsdi_view_id_val[ ] has four values, e.g., sdi_view_id_val[0 (layer 0)]=0(view 0), and sdi_view_id_val[1 (layer 1)]=0 (view 0), sdi_view_id_val[2(layer 2)]=1 (view 1), and sdi_view_id_val[3 (layer 3)]=1 (view 0).

As described above, the syntax element sdi_view_id_val[ ] in the firstSEI message can indicate a relationship between an i-th layer of aplurality of layers (e.g., layers 0-4) in the CVS and a view of aplurality of views (e.g., views 0-1) in the CVS. In an example, if thei-th layer of the plurality of layers is known, the corresponding viewof the plurality of views is determined based on the relationship. Ifthe view of the plurality of views is known, the corresponding layer(s)can be determined based on the relationship. Referring back to the aboveexample where the layers 0-3 correspond to view 0 and view 1, if thei-th layer is the layer 2, the corresponding view is determined to bethe view 1. If the view is the view 0, the corresponding layer isdetermined to be one of the layers 0-1.

The length of the sdi_view_id_val[i] syntax element (e.g., a number ofbits used to represent the syntax element sdi_view_id_val[i]) can beindicated by the syntax element sdi_view_id_len_minus1 in the first SEImessage (e.g., the SDI SEI message). The syntax elementsdi_view_id_len_minus1 plus 1 can specify the length, in bits, of thesdi_view_id_val[i] syntax element. The length of sdi_view_id_val[i] canbe equal to (sdi_view_id_len_minus1+1) bits. In an example, whensdi_multiview_info_flag is equal to 0, the value of sdi_view_id_val[i]is inferred to be equal to 0.

The variable ViewId specified by the syntax element sdi_view_id_val[i]in the first SEI message can be referred to or used by other messages(e.g., other SEI messages), such as a MAI SEI message, an SEI messageindicating depth representation information (referred to as a depthrepresentation information SEI message), and/or the like.

The syntax elements in the depth representation information SEI messagecan specify various parameters for auxiliary pictures of type AUX_DEPTH(e.g., with sdi_aux_id[i] being 2) for the purpose of processing decodedprimary and auxiliary pictures prior to rendering on a 3D display, suchas view synthesis. Based on Table 2, when the type is AUX_DEPTH, theauxiliary pictures are depth pictures. In an example, depth or disparityranges for depth pictures are specified. When present, the depthrepresentation information SEI message can be associated with one ormore layers with AuxId value equal to AUX_DEPTH. When present, the depthrepresentation information SEI message may be included in any accessunit. In an example, when present, the SEI message is included in anTRAP access unit for the purpose of random access. The informationindicated in the SEI message applies to all the pictures of eachassociated layer from the access unit containing the SEI message to thenext access unit, in decoding order, containing an SEI message of thesame type and associated with the same layer, exclusive, or to the endof the coded video sequence, whichever is earlier in decoding order.

In an example, a depth representation information SEI message includes asyntax element disparity_ref_view_id. The syntax elementdisparity_ref_view_id can use or refer to the ViewId that is specifiedby the syntax element sdi_view_id_val[i] in the first SEI message. In anexample, the syntax element disparity_ref_view_id specifies the ViewIdvalue against which the disparity values are derived.

In an example, a target layer of the plurality of layers to which thesyntax element disparity_ref_view_id applies is determined based onvalues of the syntax element sdi_view_id_val[ ] signaled.

In an example, the syntax element disparity_ref_view_id is present(e.g., is signaled) only if a minimum flag (e.g., d_min_flag) is equalto 1 or a maximum flag (e.g., d_max_flag) is equal to 1. In someexamples, the syntax element disparity_ref_view_id is useful in depthrepresentation types (e.g., depth_representation_type) 1 and 3, such asshown in Table 3. The syntax element depth_representation_type canspecify the representation definition of decoded luma samples ofauxiliary pictures as specified in Table 3. In Table 3, disparityspecifies the horizontal displacement between two texture views and Zvalue specifies the distance from a camera.

TABLE 3 Definition of depth_representation_type depth_represen-tation_type Interpretation 0 Each decoded luma sample value of anauxiliary picture represents an inverse of Z value that is uniformlyquantized into the range of 0 to 255, inclusive. 1 Each decoded lumasample value of an auxiliary picture represents disparity that isuniformly quantized into the range of 0 to 255, inclusive. 2 Eachdecoded luma sample value of an auxiliary picture represents a Z valueuniformly quantized into the range of 0 to 255, inclusive. 3 Eachdecoded luma sample value of an auxiliary picture represents anonlinearly mapped disparity, normalized in range from 0 to 255, asspecified by depth_nonlinear_representation_num_minus1 anddepth_nonlinear_representation_model[ i ]. Other values Reserved forfuture use

Table 4 shows an association between depth parameter variables andsyntax elements.

x s e n v ZNear ZNearSign ZNearExp ZNearMantissa ZNearManLen ZFarZFarSign ZFarExp ZFarMantissa ZFarManLen DMax DMaxSign DMaxExpDMaxMantissa DMaxManLen DMin DMinSign DMinExp DMinMantissa DMinManLen

The variables (e.g., ZNear) in the x column of Table 4 can be derivedfrom the respective variables (e.g., ZNearSign, ZNearExp, ZNearMantissa,and ZNearManLen) in the s, e, n and v columns of Table 4 as follows.

-   -   If the value of e is in the range of 0 to 127, exclusive, x is        set equal to (−1)^(s)×2^((e−31))×(1+n÷2^(v)).    -   Otherwise (e is equal to 0), x is set equal to        (−1)^(s)×2^(−(30+v))×n

A variable ZNear can represent a nearest depth. A value of the variableZNear can be determined as described above using values of the syntaxelements ZNearSign, ZNearExp, ZNearMantissa, ZNearManLen in the depthrepresentation information SEI message.

A variable ZFar can represent a farthest depth. A value of the variableZFar can be determined as described above using values of the syntaxelements ZFarSign, ZFarExp, ZFarMantissa, ZFarManLen in the depthrepresentation information SEI message.

A variable DMax can represent a maximum disparity. A value of thevariable DMax can be determined as described above using values of thesyntax elements DMaxSign, DMaxExp, DMaxMantissa, DMaxManLen in the depthrepresentation information SEI message.

A variable DMin can represent a minimum disparity. A value of thevariable DMin can be determined as described above using values of thesyntax elements DMinSign, DMinExp, DMinMantissa, DMinManLen in the depthrepresentation information SEI message.

The DMin and DMax values, when present, can be specified in units of aluma sample width of the coded picture with ViewId equal to ViewId ofthe auxiliary picture.

A MAI SEI message can specify various parameters of the acquisitionenvironment for the layers that may be present in a current CVS, e.g.,the CVS including the MAI SEI message. In an embodiment, intrinsiccamera parameters (e.g., a focal length, a principle point, and a skewfactor) and extrinsic camera parameters (e.g., a rotational matrix and atranslation vector) are indicated (e.g., specified), for example, bycorresponding syntax elements in the MAI SEI message. The intrinsiccamera parameters and the extrinsic camera parameters can be used toprocess decoded views prior to rendering the decoded views (e.g.,decoded pictures corresponding to the decoded views) on a 3D display.

FIG. 9 shows a syntax example (900) in a MAI SEI message that indicatesMAI according to an embodiment of the disclosure. The MAI SEI messagecan include syntax elements that are associated with the intrinsiccamera parameters where the syntax elements includesign_focal_length_x[i], exponent_focal_length_x[i],mantissa_focal_length_x[i], sign_focal_length_y[i],exponent_focal_length_y[i], mantissa_focal_length_ y[i],sign_principal_point_x[i], exponent_principal_point_[i],mantissa_principal_point_x[i], sign_principal_point_y[i],exponent_principal_pointy[i], mantissa_principal_point_y[i],sign_skew_factor[i], exponent_skew_factor[i], andmantissa_skew_factor[i].

The syntax elements sign_focal_length_x[i], exponent_focal_length_x[i],and mantissa_focal_length x[i] can be used to determine a variablefocalLengthX[i], as shown in FIG. 10 . The syntax elementssign_focal_length_y[i], exponent_focal_length_y[i], andmantissa_focal_length_ y[i] can be used to determine a variablefocalLengthY[i], as shown in FIG. 10 . The syntax elementssign_principal_point x[i], exponent_principal_point_[i], andmantissa_principal_point_x[i] can be used to determine a variableprincipalPointX[i], as shown in FIG. 10 . The syntax elementssign_principal_point_y[i], exponent_principal_point_y[i], andmantissa_principal_point_y[i] can be used to determine a variableprincipalPointY[i], as shown in FIG. 10 . The syntax elementssign_skew_factor[i], exponent_skew_factor[i], andmantissa_skew_factor[i] can be used to determine a variableskewFactor[i], as shown in FIG. 10 .

The intrinsic camera parameters of an i-th camera can include thevariables focalLengthX[i], focalLengthY[i], principalPointX[i],principalPointY[i], and skewFactor[i]. The variables focalLengthX[i] andfocalLengthY[i] can indicate a focal length of the i-th camera in thehorizontal direction and the vertical direction, respectively. Thevariables principalPointX[i] and principalPointY[i] can indicate aprincipal point of the i-th camera in the horizontal direction and thevertical direction, respectively. The variable skewFactor[i] canindicate a skew factor of the i-th camera. The intrinsic cameraparameters of the i-th camera, such as the focal length, the principlepoint, and the skew factor can indicate intrinsic properties of the i-thcamera. The intrinsic camera parameters of the i-th camera, such as thefocal length, the principle point, and the skew factor can beindependent from a location or an orientation of the i-th camera withrespect to a scene to be acquired by the i-th camera.

In an example, an intrinsic matrix or an intrinsic camera parametermatrix A[i] for the i-th camera can be determined based on thecorresponding intrinsic camera parameters, such as the focal length, theprinciple point, and the skew factor using Eq. 1.

$\begin{matrix}{{A\lbrack i\rbrack} = \begin{bmatrix}{{focalLengthX}\lbrack i\rbrack} & {{skewFacto}{r\lbrack i\rbrack}} & {princ{ipalPoint}{X\lbrack i\rbrack}} \\0 & {{focalLengthY}\lbrack i\rbrack} & {princ{ipalPoint}{Y\lbrack i\rbrack}} \\0 & 0 & 1\end{bmatrix}} & {{Eq}.1}\end{matrix}$

The MAI SEI message can include syntax elements that are associated withthe extrinsic camera parameters including sign_r[i][j][k],exponent_r[i][j][k], mantissa_r[i][j][k], sign_t[i][j],exponent_t[i][j], and mantissa_t[i][j]. The syntax elementssign_r[i][j][k], exponent_r[i][j][k], and mantissa_r[i][j][k] can beused to determine a variable rE[i][j][k], as shown in FIG. 10 . Thesyntax elements sign_t[i][j], exponent_t[i][j], and mantissa_t[i][j] canbe used to determine a variable tE[i][j], as shown in FIG. 10 .

The extrinsic camera parameters of the i-th camera can include thevariables rE[i][j][k] and tE[i][j]. The variable rE[i][j][k] canindicate an element (e.g., at [j][k]) of a rotation matrix R[i] of thei-th camera. The variable tE[i][j] can indicate a j-th element of atranslation vector T[i] of the i-th camera. The extrinsic cameraparameters of the i-th camera, such as the rotation matrix R[i] and thetranslation vector T[i] can indicate extrinsic properties of the i-thcamera. In an example, the extrinsic camera parameters of the i-thcamera, such as the rotation matrix R[i] and the translation vectorT[i], is associated with the location and/or the orientation of the i-thcamera with respect to the scene to be acquired.

In an example, the rotation matrix R[i] for the i-th camera can bedetermined based on the corresponding extrinsic camera parameterrE[i][j][k] using Eq. 2.

$\begin{matrix}{{R\lbrack i\rbrack} = \begin{bmatrix}{{{{rE}\lbrack i\rbrack}\lbrack 0\rbrack}\lbrack 0\rbrack} & {{{{rE}\lbrack i\rbrack}\lbrack 0\rbrack}\lbrack 1\rbrack} & {{{{rE}\lbrack i\rbrack}\lbrack 0\rbrack}\lbrack 2\rbrack} \\{{{{rE}\lbrack i\rbrack}\lbrack 1\rbrack}\lbrack 0\rbrack} & {{{{rE}\lbrack i\rbrack}\lbrack 1\rbrack}\lbrack 1\rbrack} & {{{{rE}\lbrack i\rbrack}\lbrack 1\rbrack}\lbrack 2\rbrack} \\{{{{rE}\lbrack i\rbrack}\lbrack 2\rbrack}\lbrack 0\rbrack} & {{{{rE}\lbrack i\rbrack}\lbrack 2\rbrack}\lbrack 1\rbrack} & {{{{rE}\lbrack i\rbrack}\lbrack 2\rbrack}\lbrack 2\rbrack}\end{bmatrix}} & {{Eq}.2}\end{matrix}$

In an example, the translation vector T[i] for the i-th camera can bedetermined based on the corresponding extrinsic camera parametertE[i][j] using Eq. 3.

$\begin{matrix}{{T\lbrack i\rbrack} = \begin{bmatrix}{{{tE}\lbrack i\rbrack}\lbrack 0\rbrack} \\{{{tE}\lbrack i\rbrack}\lbrack 1\rbrack} \\{{{tE}\lbrack i\rbrack}\lbrack 2\rbrack}\end{bmatrix}} & {{Eq}.3}\end{matrix}$

FIG. 10 shows relationships between camera parameter variables (e.g.,shown in a column x) and corresponding syntax elements (e.g., shown incolumns s, e, and n) according to an embodiment of the disclosure. Eachcomponent of the intrinsic and rotation matrices and the translationvector can be obtained from the variables specified in FIG. 10 . Thesyntax elements in the column s can indicate signs of the respectivevariables in the column x. The syntax elements in the column e canindicate exponent parts of the respective variables in the column x. Thesyntax elements in the column n can indicate mantissa parts of therespective variables in the column x.

A variable (e.g., focalLengthX[i]) in the x column can be computed asfollows:

-   -   If a variable (e.g., exponent_focal_length_x[i]) in the column e        is in the range of 0 to 63, exclusive, the variable (e.g.,        focalLengthX[i]) in the x column is set equal to        (−1)^(s)×2^(e−31)×(1+n÷2 ^(v)).

Otherwise (the variable in the column e is equal to 0), the variable inthe x column is set equal to (−1)^(s)*2^(−(30+v))×n.

In an example, the extrinsic camera parameters are specified accordingto a right-handed coordinate system where an upper left corner of apicture (or an image) is the origin (e.g., the (0, 0) coordinate) of theright-handed coordinate system. Other corners of the picture (or theimage) can have non-negative coordinates. In an example, a 3-dimensional(3D) world point wP (e.g., the position of wP is specified with a 3Dcoordinate [ x y z]) is mapped to a 2-dimensional (2D) camera pointcP[i] for the i-th camera. The camera point cP[i] can be specified by a2D coordinate [u v 1] for the i-th camera according to Eq. 4.

s×cP[i]=A[i]×R ⁻¹[i]×(wP−T[i])   Eq. 4

where A[i] is the intrinsic camera parameter matrix for the i-th camera,R⁻¹[i] denotes the inverse rotation matrix of the rotation matrix R[i]for the i-th camera, T[i] denotes the translation vector for the i-thcamera and s (a scalar value) is an arbitrary scale factor chosen tomake the third coordinate of cP[i] equal to 1. The elements of A[i],R[i] and T[i] are determined according to the syntax elements signaledin the MAI SEI message, such as described above.

In related video coding technologies, such as in HEVC/H.265, a targetlayer to which the MAI SEI message is applied can be specified by thefollowing semantics. An index i (e.g., the index i in focalLengthX[i] orin exponent_focal_length_x[i]) refers to the syntax elements andvariables that apply to the layer with a network abstraction layer (NAL)unit header layer identifier (e.g., nuh_layer_id) of a layer equal to ani-th element in a nesting layer ID list (e.g.,nestingLayerIdList[0][i]).

In some video coding technologies, such as VSEI, a target layer that isassociated with the intrinsic camera parameters (e.g., focalLengthX[i],focalLengthY[i], principalPointX[i], principalPointY[i], skewFactor[i],and/or A[i]) and/or the extrinsic camera parameters (e.g., R[i], T[i],and/or elements in R[i] and T[i]) indicated by the MAI SEI message isnot clearly specified.

According to an embodiment of the disclosure, the target layer that isassociated with the intrinsic camera parameters and the extrinsic cameraparameters indicated by the MAI SEI message (e.g., the MAI SEI messagein the VSEI) can be specified based on another SEI message, such as asyntax element (e.g., sdi_view_id_val[ ]) in the first SEI message(e.g., the SDI SEI message). In an example, the target layer is a layerof the plurality of layers in the current CVS where a corresponding viewof the target layer is indicated by the syntax elementsdi_view_id_val[i] in the first SEI message (e.g., the SDI SEI message).

In an embodiment, in the semantics above with reference to FIGS. 9 and10 , the index i refers to the syntax elements and variables (e.g., thesyntax elements and variables in FIGS. 9-10 ) that apply to the j-thlayer in the CVS with sdi_view_id_val[j] equal to sdi_view_id_val[i].

In an embodiment, in the semantics above with reference to FIGS. 9 and10 , the index i refers to the syntax elements and variables (e.g., thesyntax elements and variables in FIGS. 9-10 ) that apply to the layer inthe CVS with ViewId equal to sdi_view_id_val[i].

According to an embodiment of the disclosure, the first SEI message(e.g., the SDI SEI message) can be received. The first SEI message caninclude the SDI of the plurality of views in the multiview bitstreamincluding the CVS (e.g., the current CVS). The CVS can include aplurality of layers. Values of a first syntax element sdi_view_id_val[ ]in the first SEI message can be determined. Each value of the firstsyntax element sdi_view_id_val[ ] can correspond to a respective layerin the plurality of layers. Each value of the first syntax elementsdi_view_id_val[ ] in the first SEI message can specify a viewidentifier (ViewId) of the respective layer in the plurality of layer.In an example, four values (e.g., 0, 0, 1, and 1) of the syntax elementsdi_view_id_val[ ] are determined with an index being 0-3 correspondingto layers 0-3, respectively. The layer 0 has a ViewId ofsdi_view_id_val[0] (e.g., 0 for view 0). The layer 1 has a ViewId ofsdi_view_id_val[1] (e.g., 0 for view 0). The layer 2 has a ViewId ofsdi_view_id_val[2] (e.g., 1 for view 1). The layer 3 has a ViewId ofsdi_view_id_val[3] (e.g., 1 for view 1).

Based on the values of the first syntax element sdi_view_id_val[ ] inthe first SEI message (e.g., the SDI SEI message), a target layer of theplurality of layers to which a second syntax element (e.g., one of thesyntax elements in FIGS. 9-10 ) of a second SEI message (e.g., the MAISEI message) applies can be determined. The second syntax element cancorrespond to a view of the plurality of views, for example, acquired bya respective camera. Referring to FIG. 9 or 10 , each syntax element(e.g., the second syntax element, such as sign_focal_length_x[i] orsign_r[i][j][k]) that is referenced by an index i indicates a cameraparameter (e.g., an intrinsic or an extrinsic parameter) of an i-thcamera. In an example, the i-th camera acquires an i-th view of theplurality of views. In some examples, each syntax element that isreferenced by the index i corresponds to the i-th view of the pluralityof views. Based on the i-th view and the relationship between theplurality of view and the plurality of layers in the CVS indicated bythe values of the first syntax element sdi_view_id_val[ ] in the firstSEI message (e.g., the SDI SEI message), the target layer of theplurality of layers to which the second syntax element of the second SEImessage (e.g., the MAI SEI message) applies can be determined. Forexample, the index i in sign_focal_length_x[0] is 0,sign_focal_length_x[0] of the 0-th camera and 0-th view corresponds tothe target layer of layer 0 or layer 1.

In an example, the target layer is determined based on the values of thefirst syntax element sdi_view_id_val[ ] in the first SEI message and aViewId of the view of the plurality of views. For example, the index iin sign_focal_length_x[0] is 0, a ViewId of sign_focal_length_x[0] ofthe 0-th camera and 0-th view is 0. The ViewId of 0 is equal tosdi_view_id_val[0] or sdi_view_id_val[1]. Thus, the target layer islayer 0 or layer 1.

In an example, the second SEI message includes the MAI. The secondsyntax element indicates view acquisition information of the view of theplurality of views. The view acquisition information can include anintrinsic camera parameter or an extrinsic camera parameter that is usedto acquire the view of the plurality of views.

One or more layers can correspond to a view of the plurality of views.In an example, the one or more layers corresponding to the view of theplurality of views has an identical value of the variable ViewId.

When a MAI SEI message is present in an AU (e.g., any AU) of a CVS, theMAI SEI message can be present for the first AU of the CVS. According toan embodiment of the disclosure, the MAI SEI message applies to first AUof the CVS. In an example, all MAI SEI messages in the CVS can have thesame content.

When a MAI SEI message is present, the MAI SEI message that applies tothe current layer can be included in an access unit that includes anIRAP picture that is the first picture of a CLVS of the current layer.The information signaled in the MAI SEI message can apply to the CLVS.

In an example, the MAI SEI message cannot be contained in a scalablenesting SEI message. The MAI SEI message is not included in the scalablenesting SEI message.

In an embodiment, when the CVS does not include an SDI SEI message, theCVS does not include an MAI SEI message. The MAI SEI message is includedin the CVS based on the SDI SEI message being included in the CVS.

When an AU includes both an SDI SEI message and an MAI SEI message, theSDI SEI message can precede the MAI SEI message, for example, in adecoding order.

When the SDI SEI message and the MAI SEI message apply to an AU, the SDISEI message can precede the MAI SEI message, for example, in thedecoding order.

Some of the views for which the MAI is included in an MAI SEI messagemay not be present in the current CVS.

As described in the disclosure, the MAI SEI message is included in theCVS based on the SDI SEI message being included in the CVS. Thedetermining the values of the first syntax element sdi_view_id_val[ ] inthe SDI SEI message and the determining the target layer are performedbased on the SDI SEI message and the MAI message being included in theCVS.

FIG. 11 shows a flow chart outlining an encoding process (1100)according to an embodiment of the disclosure. In various embodiments,the process (1100) is executed by processing circuitry, such as theprocessing circuitry in the terminal devices (310), (320), (330) and(340), processing circuitry that performs functions of a video encoder(e.g., (403), (603), (703)), or the like. In some embodiments, theprocess (1100) is implemented in software instructions, thus when theprocessing circuitry executes the software instructions, the processingcircuitry performs the process (1100). The process starts at (S1101),and proceeds to (S1110).

At (S1110), a first supplemental enhancement information (SEI) messageindicating scalability dimension information (SDI) can be generated, asdescribed with reference to Table 1. The first SEI message includes theSDI of a plurality of views in a multiview bitstream. The multiviewbitstream can include a coded video sequence (CVS) with a plurality oflayers. The plurality of views corresponds to the plurality of layers.

As described with reference to Table 1, the first SEI message caninclude a first syntax element sdi_view_id_val[ ]. Each value of thefirst syntax element sdi_view_id_val[ ] can correspond to a respectivelayer in the plurality of layers. The first syntax elementsdi_view_id_val[i] can specify a variable ViewId value of the i-th layerin the CVS. The variable ViewId indicates a view ID of a view in theplurality of views.

At (S1120), a second SEI message indicating multiview acquisitioninformation (MAI) can be generated. The second SEI message includes asecond syntax element indicating view acquisition information of a viewof the plurality of views, as described in FIGS. 9-10 .

Based on the values of the first syntax element sdi_view_id_val[ ] inthe first SEI message, a target layer of the plurality of layers towhich the second syntax element of the second SEI message applies can bedetermined. The second syntax element corresponds to a view of theplurality of views.

In an example, an index i refers to syntax elements and variablesindicated in the second SEI message that apply to the j-th layer in theCVS with sdi_view_id_val[j] equal to sdi_view_id_val[i].

In an example, an index i refers to the syntax elements and variablesindicated in the second SEI message that apply to the layer in the CVSwith a ViewId equal to sdi_view_id_val[i].

At (S1130), the first SEI message and the second SEI message can beincluded in the multiview bitstream.

The process (1100) proceeds to (S1199), and terminates.

The process (1100) can be suitably adapted to various scenarios andsteps in the process (1100) can be adjusted accordingly. One or more ofthe steps in the process (1100) can be adapted, omitted, repeated,and/or combined. Any suitable order can be used to implement the process(1100). Additional step(s) can be added.

FIG. 12 shows a flow chart outlining a decoding process (1200) accordingto an embodiment of the disclosure. In various embodiments, the process(1200) is executed by processing circuitry, such as the processingcircuitry in the terminal devices (310), (320), (330) and (340), theprocessing circuitry that performs functions of the video encoder (403),the processing circuitry that performs functions of the video decoder(410), the processing circuitry that performs functions of the videodecoder (510), the processing circuitry that performs functions of thevideo encoder (603), and the like. In some embodiments, the process(1200) is implemented in software instructions, thus when the processingcircuitry executes the software instructions, the processing circuitryperforms the process (1200). The process starts at (S1201), and proceedsto (S1210).

At (S1210), a first supplemental enhancement information (SEI) messageincluding scalability dimension information (SDI) can be received. Thefirst SEI message can include the SDI of a plurality of views in amultiview bitstream including a coded video sequence (CVS). The CVS canhave a plurality of layers that correspond to the plurality of views.

At (S1220), a value of a first syntax element sdi_view_id_val[ ] in thefirst SEI message can be determined. The first syntax elementsdi_view_id_val[ ] can indicate a view identifier (ViewId) of a layer inthe plurality of layers. The first syntax element sdi_view_id_val[ ] inthe first SEI message can specify the ViewId of the layer in theplurality of layer.

In an example, values of the first syntax element sdi_view_id_val[ ] inthe first SEI message can be determined. Each value of the first syntaxelement sdi_view_id_val[ ] can correspond to a respective layer in theplurality of layers. For example, sdi_view_id_val[i] specifies a ViewIdvalue of an i-th layer in the CVS.

At (S1230), based on the first syntax element sdi_view_id_val[ ] in thefirst SEI message, a target layer of the plurality of layers to which asecond syntax element of a second SEI message applies can be determined.A view of the plurality of views that is associated with the secondsyntax element can be indicated by the first syntax elementsdi_view_id_val[ ].

In an example, a view identifier of the view of the plurality of viewsthat is associated with the second syntax element is equal to the valueof the first syntax element sdi_view_id_val[ ].

In an example, the second SEI message includes multiview acquisitioninformation (MAI). The second syntax element indicates view acquisitioninformation of the view of the plurality of views. The view acquisitioninformation includes an intrinsic camera parameter or an extrinsiccamera parameter that is used to acquire the view of the plurality ofviews.

In an example, the target layer is determined based on the values of thefirst syntax element sdi_view_id_val[ ] in the first SEI message and aViewId of the view of the plurality of views.

The second SEI message can apply to a first access unit of the CVS.

The second SEI message may not be included in a scalable nesting SEImessage.

In an example, the first SEI message and the second SEI message apply toan access unit, and the first SEI message precedes the second SEImessage in a decoding order.

The process (1200) proceeds to (S1299), and terminates.

The process (1200) can be suitably adapted to various scenarios andsteps in the process (1200) can be adjusted accordingly. One or more ofthe steps in the process (1200) can be adapted, omitted, repeated,and/or combined. Any suitable order can be used to implement the process(1200). Additional step(s) can be added.

In an example, the second SEI message is included in the CVS based onthe first SEI message being included in the CVS. The determining thevalues of the first syntax element and the determining the target layerare performed based on the first SEI message and the second messagebeing included in the CVS.

In an example, a third SEI message indicating depth representationinformation is decoded. The ViewId indicated by the first syntax elementsdi_view_id_val[ ] is referenced by a third syntax element in the thirdSEI message.

Embodiments in the disclosure may be used separately or combined in anyorder. Further, each of the methods (or embodiments), an encoder, and adecoder may be implemented by processing circuitry (e.g., one or moreprocessors or one or more integrated circuits). In one example, the oneor more processors execute a program that is stored in a non-transitorycomputer-readable medium.

The techniques described above, can be implemented as computer softwareusing computer-readable instructions and physically stored in one ormore computer-readable media. For example, FIG. 13 shows a computersystem (1300) suitable for implementing certain embodiments of thedisclosed subject matter.

The computer software can be coded using any suitable machine code orcomputer language, that may be subject to assembly, compilation,linking, or like mechanisms to create code comprising instructions thatcan be executed directly, or through interpretation, micro-codeexecution, and the like, by one or more computer central processingunits (CPUs), Graphics Processing Units (GPUs), and the like.

The instructions can be executed on various types of computers orcomponents thereof, including, for example, personal computers, tabletcomputers, servers, smartphones, gaming devices, internet of thingsdevices, and the like.

The components shown in FIG. 13 for computer system (1300) are exemplaryin nature and are not intended to suggest any limitation as to the scopeof use or functionality of the computer software implementingembodiments of the present disclosure. Neither should the configurationof components be interpreted as having any dependency or requirementrelating to any one or combination of components illustrated in theexemplary embodiment of a computer system (1300).

Computer system (1300) may include certain human interface inputdevices. Such a human interface input device may be responsive to inputby one or more human users through, for example, tactile input (such as:keystrokes, swipes, data glove movements), audio input (such as: voice,clapping), visual input (such as: gestures), olfactory input (notdepicted). The human interface devices can also be used to capturecertain media not necessarily directly related to conscious input by ahuman, such as audio (such as: speech, music, ambient sound), images(such as: scanned images, photographic images obtain from a still imagecamera), video (such as two-dimensional video, three-dimensional videoincluding stereoscopic video).

Input human interface devices may include one or more of (only one ofeach depicted): keyboard (1301), mouse (1302), trackpad (1303), touchscreen (1310), data-glove (not shown), joystick (1305), microphone(1306), scanner (1307), camera (1308).

Computer system (1300) may also include certain human interface outputdevices. Such human interface output devices may be stimulating thesenses of one or more human users through, for example, tactile output,sound, light, and smell/taste. Such human interface output devices mayinclude tactile output devices (for example tactile feedback by thetouch-screen (1310), data-glove (not shown), or joystick (1305), butthere can also be tactile feedback devices that do not serve as inputdevices), audio output devices (such as: speakers (1309), headphones(not depicted)), visual output devices (such as screens (1310) toinclude CRT screens, LCD screens, plasma screens, OLED screens, eachwith or without touch-screen input capability, each with or withouttactile feedback capability—some of which may be capable to output twodimensional visual output or more than three dimensional output throughmeans such as stereographic output; virtual-reality glasses (notdepicted), holographic displays and smoke tanks (not depicted)), andprinters (not depicted).

Computer system (1300) can also include human accessible storage devicesand their associated media such as optical media including CD/DVD ROM/RW(1320) with CD/DVD or the like media (1321), thumb-drive (1322),removable hard drive or solid state drive (1323), legacy magnetic mediasuch as tape and floppy disc (not depicted), specialized ROM/ASIC/PLDbased devices such as security dongles (not depicted), and the like.

Those skilled in the art should also understand that term “computerreadable media” as used in connection with the presently disclosedsubject matter does not encompass transmission media, carrier waves, orother transitory signals.

Computer system (1300) can also include an interface (1354) to one ormore communication networks (1355). Networks can for example bewireless, wireline, optical. Networks can further be local, wide-area,metropolitan, vehicular and industrial, real-time, delay-tolerant, andso on. Examples of networks include local area networks such asEthernet, wireless LANs, cellular networks to include GSM, 3G, 4G, 5G,LTE and the like, TV wireline or wireless wide area digital networks toinclude cable TV, satellite TV, and terrestrial broadcast TV, vehicularand industrial to include CANBus, and so forth. Certain networkscommonly require external network interface adapters that attached tocertain general purpose data ports or peripheral buses (1349) (such as,for example USB ports of the computer system (1300)); others arecommonly integrated into the core of the computer system (1300) byattachment to a system bus as described below (for example Ethernetinterface into a PC computer system or cellular network interface into asmartphone computer system). Using any of these networks, computersystem (1300) can communicate with other entities. Such communicationcan be uni-directional, receive only (for example, broadcast TV),uni-directional send-only (for example CANbus to certain CANbusdevices), or bi-directional, for example to other computer systems usinglocal or wide area digital networks. Certain protocols and protocolstacks can be used on each of those networks and network interfaces asdescribed above.

Aforementioned human interface devices, human-accessible storagedevices, and network interfaces can be attached to a core (1340) of thecomputer system (1300).

The core (1340) can include one or more Central Processing Units (CPU)(1341), Graphics Processing Units (GPU) (1342), specialized programmableprocessing units in the form of Field Programmable Gate Areas (FPGA)(1343), hardware accelerators for certain tasks (1344), graphicsadapters (1350), and so forth. These devices, along with Read-onlymemory (ROM) (1345), Random-access memory (1346), internal mass storagesuch as internal non-user accessible hard drives, SSDs, and the like(1347), may be connected through a system bus (1348). In some computersystems, the system bus (1348) can be accessible in the form of one ormore physical plugs to enable extensions by additional CPUs, GPU, andthe like. The peripheral devices can be attached either directly to thecore's system bus (1348), or through a peripheral bus (1349). In anexample, the screen (1310) can be connected to the graphics adapter(1350). Architectures for a peripheral bus include PCI, USB, and thelike.

CPUs (1341), GPUs (1342), FPGAs (1343), and accelerators (1344) canexecute certain instructions that, in combination, can make up theaforementioned computer code. That computer code can be stored in ROM(1345) or RAM (1346). Transitional data can be stored in RAM (1346),whereas permanent data can be stored for example, in the internal massstorage (1347). Fast storage and retrieve to any of the memory devicescan be enabled through the use of cache memory, that can be closelyassociated with one or more CPU (1341), GPU (1342), mass storage (1347),ROM (1345), RAM (1346), and the like.

The computer readable media can have computer code thereon forperforming various computer-implemented operations. The media andcomputer code can be those specially designed and constructed for thepurposes of the present disclosure, or they can be of the kind wellknown and available to those having skill in the computer software arts.

As an example and not by way of limitation, the computer system havingarchitecture (1300), and specifically the core (1340) can providefunctionality as a result of processor(s) (including CPUs, GPUs, FPGA,accelerators, and the like) executing software embodied in one or moretangible, computer-readable media. Such computer-readable media can bemedia associated with user-accessible mass storage as introduced above,as well as certain storage of the core (1340) that are of non-transitorynature, such as core-internal mass storage (1347) or ROM (1345). Thesoftware implementing various embodiments of the present disclosure canbe stored in such devices and executed by core (1340). Acomputer-readable medium can include one or more memory devices orchips, according to particular needs. The software can cause the core(1340) and specifically the processors therein (including CPU, GPU,FPGA, and the like) to execute particular processes or particular partsof particular processes described herein, including defining datastructures stored in RAM (1346) and modifying such data structuresaccording to the processes defined by the software. In addition or as analternative, the computer system can provide functionality as a resultof logic hardwired or otherwise embodied in a circuit (for example:accelerator (1344)), which can operate in place of or together withsoftware to execute particular processes or particular parts ofparticular processes described herein. Reference to software canencompass logic, and vice versa, where appropriate. Reference to acomputer-readable media can encompass a circuit (such as an integratedcircuit (IC)) storing software for execution, a circuit embodying logicfor execution, or both, where appropriate. The present disclosureencompasses any suitable combination of hardware and software.

Appendix A: Acronyms

JEM: joint exploration modelVVC: versatile video codingBMS: benchmark set

MV: Motion Vector HEVC: High Efficiency Video Coding SEI: SupplementaryEnhancement Information VUI: Video Usability Information GOPs: Groups ofPictures TUs: Transform Units, PUs: Prediction Units CTUs: Coding TreeUnits CTBs: Coding Tree Blocks PBs: Prediction Blocks HRD: HypotheticalReference Decoder SNR: Signal Noise Ratio CPUs: Central Processing UnitsGPUs: Graphics Processing Units CRT: Cathode Ray Tube LCD:Liquid-Crystal Display OLED: Organic Light-Emitting Diode CD: CompactDisc DVD: Digital Video Disc ROM: Read-Only Memory RAM: Random AccessMemory ASIC: Application-Specific Integrated Circuit PLD: ProgrammableLogic Device LAN: Local Area Network

GSM: Global System for Mobile communications LTE: Long-Term Evolution

CANBus: Controller Area Network Bus USB: Universal Serial Bus PCI:Peripheral Component Interconnect FPGA: Field Programmable Gate Areas

SSD: solid-state drive

IC: Integrated Circuit CU: Coding Unit R-D: Rate-Distortion

While this disclosure has described several exemplary embodiments, thereare alterations, permutations, and various substitute equivalents, whichfall within the scope of the disclosure. It will thus be appreciatedthat those skilled in the art will be able to devise numerous systemsand methods which, although not explicitly shown or described herein,embody the principles of the disclosure and are thus within the spiritand scope thereof.

What is claimed is:
 1. A method for video decoding in a video decoder,comprising: receiving a first supplemental enhancement information (SEI)message including scalability dimension information (SDI), the first SEImessage including SDI of a plurality of views in a multiview bitstreamincluding a coded video sequence (CVS) with a plurality of layers;determining a value of a first syntax element sdi_view_id_val[ ] in thefirst SEI message, the first syntax element sdi_view_id_val[ ]indicating a view identifier (ViewId) of a layer in the plurality oflayers; and determining, based on the first syntax elementsdi_view_id_val[ ] in the first SEI message, a target layer of theplurality of layers to which a second syntax element of a second SEImessage applies, a view of the plurality of views that is associatedwith the second syntax element being indicated by the first syntaxelement sdi_view_id_val[ ].
 2. The method of claim 1, wherein the firstsyntax element sdi_view_id_val[ ] in the first SEI message specifies theViewId of the layer in the plurality of layer.
 3. The method of claim 2,wherein a view identifier of the view of the plurality of views that isassociated with the second syntax element is equal to the value of thefirst syntax element sdi_view_id_val[ ].
 4. The method of claim 1,wherein the second SEI message includes multiview acquisitioninformation (MAI), the second syntax element indicates view acquisitioninformation of the view of the plurality of views, and the viewacquisition information includes an intrinsic camera parameter or anextrinsic camera parameter that is used to acquire the view of theplurality of views.
 5. The method of claim 1, wherein the second SEImessage applies to a first access unit of the CVS.
 6. The method ofclaim 1, wherein the second SEI message is not included in a scalablenesting SEI message.
 7. The method of claim 1, wherein the second SEImessage is included in the CVS based on the first SEI message beingincluded in the CVS, and the determining the value and the determiningthe target layer are performed based on the first SEI message and thesecond SEI message being included in the CVS.
 8. The method of claim 1,wherein the first SEI message and the second SEI message apply to anaccess unit, and the first SEI message precedes the second SEI messagein a decoding order.
 9. The method of claim 1, wherein a third SEImessage indicating depth representation information is decoded, theViewId indicated by the first syntax element sdi_view_id_val[ ] isreferenced by a third syntax element in the third SEI message.
 10. Anapparatus for video decoding, comprising: processing circuitryconfigured to: receive a first supplemental enhancement information(SEI) message including scalability dimension information (SDI), thefirst SEI message including SDI of a plurality of views in a multiviewbitstream including a coded video sequence (CVS) with a plurality oflayers; determine a value of a first syntax element sdi_view_id_val[ ]in the first SEI message, the first syntax element sdi_view_id_val[ ]indicating a view identifier (ViewId) of a layer in the plurality oflayers; and determine, based on the first syntax elementsdi_view_id_val[ ] in the first SEI message, a target layer of theplurality of layers to which a second syntax element of a second SEImessage applies, a view of the plurality of views that is associatedwith the second syntax element being indicated by the first syntaxelement sdi_view_id_val[ ].
 11. The apparatus of claim 10, wherein thefirst syntax element sdi_view_id_val[ ] in the first SEI messagespecifies the ViewId of the layer in the plurality of layer.
 12. Theapparatus of claim 11, wherein a view identifier of the view of theplurality of views that is associated with the second syntax element isequal to the value of the first syntax element sdi_view_id_val[ ]. 13.The apparatus of claim 10, wherein the second SEI message includesmultiview acquisition information (MAI), the second syntax elementindicates view acquisition information of the view of the plurality ofviews, and the view acquisition information includes an intrinsic cameraparameter or an extrinsic camera parameter that is used to acquire theview of the plurality of views.
 14. The apparatus of claim 10, whereinthe second SEI message applies to a first access unit of the CVS. 15.The apparatus of claim 10, wherein the second SEI message is notincluded in a scalable nesting SEI message.
 16. The apparatus of claim10, wherein the second SEI message is included in the CVS based on thefirst SEI message being included in the CVS, and the processingcircuitry is configured to perform the determining the value and thedetermining the target layer based on the first SEI message and thesecond SEI message being included in the CVS.
 17. The apparatus of claim10, wherein the first SEI message and the second SEI message apply to anaccess unit, and the first SEI message precedes the second SEI messagein a decoding order.
 18. The apparatus of claim 10, wherein theprocessing circuitry is configured to decode a third SEI message thatindicates depth representation information, the ViewId indicated by thefirst syntax element sdi_view_id_val[ ] being referenced by a thirdsyntax element in the third SEI message.
 19. A non-transitorycomputer-readable storage medium storing a program executable by atleast one processor to perform: receiving a first supplementalenhancement information (SEI) message including scalability dimensioninformation (SDI), the first SEI message including SDI of a plurality ofviews in a multiview bitstream including a coded video sequence (CVS)with a plurality of layers; determining a value of a first syntaxelement sdi_view_id_val[ ] in the first SEI message, the first syntaxelement sdi_view_id_val[ ] indicating a view identifier (ViewId) of alayer in the plurality of layers; and determining, based on the firstsyntax element sdi_view_id_val[ ] in the first SEI message, a targetlayer of the plurality of layers to which a second syntax element of asecond SEI message applies, a view of the plurality of views that isassociated with the second syntax element being indicated by the firstsyntax element sdi_view_id_val[ ].
 20. The non-transitorycomputer-readable storage medium of claim 19, wherein the first syntaxelement sdi_view_id_val[ ] in the first SEI message specifies the ViewIdof the layer in the plurality of layer